JP7169507B2 - power converter - Google Patents

Description

The present invention relates to a power converter such as an inverter having a function of detecting short-circuit failures and open-circuit failures of semiconductor switching elements.

2. Description of the Related Art Conventionally, various techniques have been proposed for diagnosing short-circuit failures and open-circuit failures of semiconductor switching elements that constitute inverters and the like.
For example, in Patent Document 1, when the DC voltage of the inverter is below a predetermined value, the switching element of the inverter is selectively turned ON. A failure diagnosis method for detecting the presence or absence of

Further, Patent Literature 2 describes a failure diagnosis method for switching elements in a motor drive system using an inverter.
Fig. ₁ is a block diagram of this motor drive system, E1 is a DC power supply, SW1 is an initial charging relay, _R1 is _a current limiting resistor, _SW2 is a main relay, C1 is a capacitor such as _a film capacitor, INV is a three-phase inverter main circuit composed of semiconductor switching elements _Qu , _Qv , _Qw , _Qx , _Qy , and _Qz , and M is a three-phase inverter in which the output voltage of the main circuit INV is applied to the stator winding. motor.

In the control device for driving the switching elements Q _u , Q _v , Q _w , Q _x , Q _y , and Q _z , the output current of the main circuit INV is detected by the current detector 11 and the alternating current detection circuit 12 to diagnose failures. It is input to the part 15 . Also, the DC input voltage of the main circuit INV is detected by the voltage detector 13 and the DC intermediate voltage detection circuit 14 and input to the fault diagnosis section 15 . The fault diagnosis unit 15 has a function of diagnosing the presence or absence of short-circuit faults and open-circuit faults of the switching elements Q _u , Q _v , Q _w , Q _x , Q _y , and Q _z , and controls opening and closing of the relays SW ₁ and SW ₂ . and a function of generating a control command for the gate drive circuit 17. The gate drive circuit 17 generates gate signals for the switching elements _Qu , _Qv , _Qw , _Qx , _Qy , and _Qz in accordance with the control command. Output.

The failure diagnosis processing in this prior art will be described with reference to the flow chart of FIG.
Initial charging relay SW1 in FIG. ₁ is _turned ON to start initial charging of capacitor C1 (step _S10 ). ) and start monitoring the output current of the main circuit INV.
If the DC intermediate voltage does not reach a predetermined voltage within a predetermined period of time from the start of time measurement (S11 No), the fault diagnosis unit 15 determines that each phase It is determined that at least one of the switching elements in the upper arm of 1 and the switching element in the lower arm of the same phase has a short-circuit failure (a short circuit exists between the DC bus lines) (S12). After that, the initial charging relay SW1 is turned off (S13), the short _- circuit fault is displayed and the host controller is notified, and the process is terminated by prohibiting the shift to normal operation (S14).

When the DC intermediate voltage reaches a predetermined voltage within a predetermined time from the start of time measurement (S11 Yes), the fault diagnosis unit 15 diagnoses that there is no short-circuit fault, and determines whether or not the DC intermediate voltage has reached a predetermined diagnostic voltage. It judges (S15). Then, when the DC intermediate voltage becomes equal to or higher than the diagnostic voltage, the initial charge relay SW1 is turned OFF (S15 Yes, S16), and a _minute pulse is applied from the gate drive circuit 17 so as to turn ON each switching element for a short period of time (S17). ), the processing after step S18 is performed while switching the switching element to be turned ON.

The failure diagnosis unit 15 determines whether or not the DC intermediate voltage drop rate _per unit time while the switching element is ON is larger than a predetermined value slightly larger than the voltage drop rate due to natural discharge of the capacitor C1. (S18). If the rate of decrease is smaller than the predetermined value (No in S18), the fault diagnosis section 15 determines that the switching elements of all the arms opposite to the arm containing the turned-on switching element are not short-circuited. After that, the failure diagnosis unit 15 returns to the process of step S17, and performs the processes from step S18 onward for all the switching elements while sequentially switching the switching elements to be turned on.

If the drop rate of the DC intermediate voltage is greater than a predetermined value (Yes in S18), and if the output current of all phases is zero (Yes in S19), the failure diagnosis unit 15 detects the arm including the switching element to which the minute pulse is applied. It is determined that the switching element of the opposite arm of the same phase is short-circuited (S20). If the output current of all phases is not zero (S19 No), it is determined that at least one switching element in the opposite arm of the phase different from the arm containing the switching element to which the minute pulse is applied has a short-circuit failure. (S21).

In step S<b>21 , the fault diagnosis unit 15 identifies the switching element having the short-circuit fault from the phase whose output current is not zero. For example, if the W-phase output current is zero and the U-phase and V-phase output currents are not zero when the U-phase upper arm switching element is turned ON, the V-phase lower arm switching element has a short-circuit fault. I judge. If the V-phase output current is zero and the U-phase and W-phase output currents are not zero, the switching element in the lower arm of the W-phase short-circuits. It is determined that the switching elements of both the phase lower arm and the W phase lower arm are short-circuited.
Next, the fault diagnosis unit 15 displays the short-circuit fault and notifies the host controller and the like, prohibits the shift to normal operation, and terminates the process (S22).

Further, in step S18, if it is determined that the DC intermediate voltage drop rate is smaller than the predetermined value (S18 No) and none of the switching elements have a short-circuit failure, the processing from step S23 onward, which is an open-circuit failure diagnosis, is performed. conduct. The failure diagnosis unit 15 applies a minute pulse to turn ON the upper arm switching element of any phase and the lower arm switching element of a different phase from the gate drive circuit 17 (S23). Then, the failure diagnosis unit 15 repeats the processing of steps S24 to S26 for each pair while sequentially switching the pair of switching elements to which pulses are applied.

When the DC intermediate voltage drop rate during the period in which the minute pulse is applied to the two switching elements is larger than _a predetermined value (voltage drop rate due to natural discharge of the capacitor C1), the failure diagnosis unit 15 , it is determined that one of the two switching elements has an open failure (S25), and the open failure is displayed and notified to prohibit the shift to normal operation (S26).
This is because the switching element with the open fault does not short-circuit between the collector and the emitter even if the ON pulse is given, and at least one of the two switching elements to which the minute pulse is given has the open fault. In this case, no current flows through the stator windings of the motor M, and the capacitor C1 maintains natural discharge. Therefore, steps S25 and S26 are executed when the DC intermediate voltage drop rate is smaller than _a predetermined value. is.

Further, when the drop rate of the DC intermediate voltage is smaller than the predetermined value (S24 Yes), the failure diagnosis unit 15 determines that neither of the two switching elements to which the minute pulse is applied has an open failure. _The charging relay SW1 is turned ON again (S27). As _a result, the initial charging of the capacitor C1 is resumed and the DC intermediate voltage rises.
When the DC intermediate voltage reaches a predetermined voltage, the fault diagnosis unit 15 turns _on the main relay SW2 by the relay driving circuit 16 (S29), and the capacitor C1 is completely charged through the _main relay _SW2 . When the charging of the capacitor C1 is completed, the fault diagnosis unit 15 sends _a control command to the gate drive circuit 17 to permit normal operation (S30).

As described above, in the motor drive system of Patent Document 2, the presence or absence of a short-circuit fault in all switching elements is diagnosed ( _first short-circuit Diagnosis of short-circuit failure and open-circuit failure of the switching element (second short-circuit failure diagnosis and open _- circuit failure diagnosis) is performed with the capacitor C1 and the _main circuit INV disconnected from the DC power supply E1. ing.
Since the diagnosis is performed while the DC voltage of the inverter is low in this way, even if the upper and lower arms are short-circuited due to a short circuit of the switching element, there is no fear that the normal switching element will be destroyed by the high voltage.

JP 2004-357437 A (paragraphs [0009] to [0019], FIG. 1, etc.) JP 2017-163714 A (paragraphs [0029] to [0064], FIG. 2, etc.)

According to the conventional technique described in Patent Document 1, it is possible to detect the presence or absence of a short-circuit fault or an open-circuit fault in a switching element, but it is impossible to specify the switching element in which these faults have occurred.
Further, in the conventional technology described in Patent Document 2, while the switching element having the short circuit failure can be identified by the steps S20 and S21 described above, if the number of phases of the inverter is n (n is an integer of 3 or more), the short circuit There is a problem that 2n judgments are necessary for diagnosing a failure, and the diagnosis time becomes long in the case of a polyphase inverter.
Furthermore, in the diagnosis after step S23 in Patent Document 2, there is also a problem that the switching element in which the open failure has occurred cannot be identified.

Therefore, the problem to be solved by the present invention is to provide a power conversion device that detects the presence or absence of failures such as open sticking with a small number of determinations and also enables specification of switching elements in which open sticking has occurred.

In order to solve the above-mentioned problems, the invention according to claim 1 is a main circuit which is connected to both ends of a capacitor which is charged from a DC power source via switching means, and which is formed by connecting a plurality of switching elements in a bridge. and a control circuit that generates a drive signal for turning on and off the switching element,
The control circuit is
The amount of change in the voltage across the capacitor when a test is conducted in which the upper arm switching element and the lower arm switching element of different phases in the main circuit are combined and these two switching elements are simultaneously turned on. performing a process of determining that at least one of the two switching elements is stuck open when the value is below a specified value and storing the test failure data;
Based on the failure data obtained by executing the processing for all the switching elements of the main circuit, it is determined that any switching element is stuck open,
When there is only one failed data,
The test and the failure data are stored by combining the switching element of the upper arm that constitutes the failure data and the switching element of the lower arm of the other phase, and the switching of the lower arm that constitutes the failure data. By combining the element and the switching element of the upper arm of the other phase, performing the test and storing the failure data, n+2 (n is the number of phases of the main circuit) pass/fail data are generated, and the pass/fail data is compared with a failure map prepared in advance to identify the switching element stuck open .

The invention according to claim 2 comprises a capacitor that is charged from a DC power source via switching means, a main circuit that is connected to both ends of the capacitor and that is formed by connecting a plurality of switching elements in a bridge, and a switching element that is turned on. , and a control circuit for generating a drive signal for turning off,
The control circuit is
When the output current of one phase becomes zero in a test in which an upper arm switching element and a lower arm switching element of different phases in the main circuit are combined and these two switching elements are turned on simultaneously, the above-mentioned Determining that at least one of the two switching elements is stuck open and storing the test failure data,
Based on the failure data obtained by executing the processing for all the switching elements of the main circuit, it is determined that any switching element is stuck open ,
When there is only one failed data,
The test and the failure data are stored by combining the switching element of the upper arm that constitutes the failure data and the switching element of the lower arm of the other phase, and the switching of the lower arm that constitutes the failure data. By combining the element and the switching element of the upper arm of the other phase, performing the test and storing the failure data, n+2 (n is the number of phases of the main circuit) pass/fail data are generated, and the pass/fail data is compared with a failure map prepared in advance to identify the switching element stuck open .

The invention according to claim 3 is the power conversion device according to claim 1 or 2 ,
The control circuit charges the capacitor when it determines that none of the two switching elements turned on at the same time is stuck open, and charges the capacitor when the voltage across the capacitor reaches a DC voltage specified value or more. It is characterized by stopping .

The invention according to claim 4 is the power conversion device according to claim 1 ,
When the control circuit determines that one of the switching elements is stuck open, it selects all the switching elements of the main circuit according to a combination different from the combination of the two switching elements in claim 1. A fault map in which 2n pass/fail data (where n is the number of phases of the main circuit) is generated by performing the test and storing the fail data for two switching elements, and the pass/fail data is prepared in advance. It is characterized in that the switching element that is open and fixed is specified by collating with .

The invention according to claim 5 is the power conversion device according to claim 2,
The control circuit is
Two switching elements each selected by a combination different from the combination of the two switching elements in claim 2 for all the switching elements of the main circuit when it is determined that any one of the switching elements is stuck open. By performing the test and saving the failure data, 2n (n is the number of phases of the main circuit) pass/fail data are generated, and the pass/fail data is compared with a prepared failure map. It is characterized by specifying a switching element stuck open.

In the present invention, in the case of an n-phase inverter, it is possible to detect the presence or absence of a switching element that is stuck open by making n determinations, and to specify the switching element that is stuck open.

1 is a configuration diagram of a motor drive system to which an embodiment of the invention is applied; FIG. FIG. 4 is a configuration diagram showing another example of the motor drive system to which the embodiment of the invention is applied; Fig. 4 is a flow chart showing Diagnosis 1 in an embodiment of the present invention; FIG. 4 is a flow chart showing Diagnosis 2 in an embodiment of the present invention; FIG. FIG. 10 is a diagram showing switching elements to be tested for diagnosis 2 and 3 in the embodiment of the present invention; Fig. 4 is a flow chart showing Diagnosis 3 in an embodiment of the present invention; It is a figure which shows the failure map at the time of open|release fixation occurrence of any arm of a three-phase inverter. It is a figure which shows the failure map at the time of open fixation occurrence of 1 arm of a three-phase inverter. It is explanatory drawing of 1 arm (Fig.9 (a)) and 1 leg (FIG.9(b)) of the main circuit of a three-phase inverter. 4 is a flowchart showing a failure diagnosis method described in Patent Document 2;

Embodiments of the present invention will be described below with reference to the drawings. The overall configuration of the motor drive system provided with the inverter according to this embodiment is the same as that of FIG.
As shown in FIG. 2, the present invention can also be applied to an inverter or the like in which the current detector 11 and the AC current detection circuit 12 in FIG. 1 are removed and only the DC intermediate voltage is detected to drive the switching element. be. This is because the inverter output current changes instantaneously and is difficult to measure, whereas the DC intermediate voltage changes relatively slowly and is easy to measure.

Next, the contents of diagnosis by the fault diagnosis unit 15, which is a feature of this embodiment, will be described.
This fault diagnosis is roughly divided into diagnosis 1 for detecting the presence or absence of fixed short-circuiting (continuous short-circuit fault) in the switching elements of the upper or lower arm of the inverter, and open-fixing of the switching elements in the upper or lower arm ( Diagnosis 2 for detecting the presence or absence of open circuit failure), and diagnosis 3 for specifying the corresponding switching element when the diagnosis 2 diagnoses that there is an open fixation.
The switching element of the inverter that is the target of failure diagnosis may be an IGBT shown in FIG. 1, a MOSFET or a power transistor, and the type thereof is not limited at all.

First, diagnosis 1 will be explained based on FIG. This diagnosis 1 starts with the motor M stationary and all the switching elements of the inverter main circuit INV turned off.
_First , the fault diagnosis unit 15 sends a command to the relay drive circuit 16 to turn on the initial charge relay _SW1 and charge the capacitor C1 through the resistor _R1 (step S101).

Next, it is determined whether or not the DC intermediate voltage _Vdc detected by the DC intermediate voltage detection circuit 14 has reached or exceeded a specified value A within _a predetermined period of time after the initial charging relay SW1 is turned ON ( S102). Here, the rate of increase of the DC intermediate voltage _Vdc depends _on the capacity of the resistor _R1 and the capacitor C1. However, if there are short-circuited switching elements in the upper arm and lower arm of the same phase of the main circuit INV, for example, if the switching elements Q _u and Q _x in the upper and lower arms of the U phase are short-circuited and fixed, positive and negative DC Due to the short circuit of the bus, the DC intermediate voltage _Vdc will not exceed the specified value A within the predetermined time. Further, if the upper arm switching element Q _u of the U phase and the lower arm switching element Q _y of the V phase are short-circuited and fixed, the path Q _u →the stator winding of the motor M →Q _y during the initial charging will Since the current flows, the rise of the DC intermediate voltage _Vdc becomes gradual, and it does not reach or exceed the specified value A within the predetermined time.

Therefore, if the DC intermediate voltage _Vdc does not reach or exceed the specified value _A within a predetermined period of time after the initial charging relay SW1 is turned ON (S102 No), the failure diagnosis unit 15 determines that the upper and lower arms are at least It can be determined that one or more switching elements are short-circuited (S104). In the case of PWM (pulse width modulation) control of the inverter, operation is impossible if even one arm is short-circuited. Therefore, it is determined in step S104 that _a major failure has occurred, and the initial charging relay SW1 is turned OFF to stop operation. (S105).

Steps S101, S102, S104, and 105 described above are diagnostics for the presence or absence of a short _- circuit fixation performed during initial charging of the capacitor C1. Even if there is a short-circuit fixation in the switching element, the current flowing into the _main circuit INV is limited by the resistor _R1 . _An overcurrent does not flow to the power supply E1, the motor M, etc., and it is possible to prevent the failure from spreading. Further, by setting the predetermined time and the specified value A in step S102 to be relatively low, it is possible to shorten the time required for diagnosing short-circuit fixation.

When the DC intermediate voltage _Vdc becomes equal to or higher than the specified value A within a predetermined time (Yes in S102), it is determined that there is no switching element short-circuited and fixed in the _upper and lower arms, and the initial charging relay SW1 is turned ON. to continue the initial charging of capacitor _C1 through resistor _R1 .
When there is no switching element short-circuited and fixed in the upper and lower arms, the DC intermediate voltage _Vdc continues to rise, and when this voltage _Vdc reaches or exceeds the specified value B (the DC voltage specified value in claims), the initial charging relay SW ₁ is turned off to complete the initial charging (S103 Yes, S106).

By turning off the initial charging relay SW1, the _main circuit _INV is disconnected from the DC power supply E1. At this time, the energy stored in the capacitor C1, in _other words, the _DC intermediate voltage _Vdc is limited. no. Also, if the specified value B in step S103 is set to a lower value, failure diagnosis can be performed more safely.
When the _main circuit INV is disconnected from the DC power supply E1, the change in the DC intermediate voltage _Vdc is caused _only by the natural discharge of the capacitor C1 and the discharge accompanying the fault diagnosis. Since the amount of change in voltage due to the natural discharge of the capacitor C1 can be grasped in advance, the amount of change ΔV in the DC intermediate voltage _Vdc considering the amount of voltage change due to the natural discharge of the capacitor C1 is _calculated as in step _S108 , which will be described later. By comparing _dc with a predetermined specified value C (variation specified value in claims), it is possible to detect whether or not the switching element is short-circuited.

Next, after the initial charge relay SW1 is turned off, the _upper arm switching elements of all phases are simultaneously turned on for a short period of time in order to diagnose the presence or absence of short-circuit fixation in the lower arm or upper arm (S107).
Now, all the switching elements of the lower arm should be OFF, so if there is no abnormality in the switching elements of the lower arm, no current will flow, and the amount of change ΔV _dc is _only due to the voltage drop caused by the natural discharge of the capacitor C1. is. However, if the amount of change ΔV _dc exceeds the specified value C, which is slightly larger than the amount of voltage drop due to natural discharge (No in S108), one of the switching elements in the lower arm is short-circuited and fixed, and all the switching elements in step S107 are stuck. It can be inferred that the amount of change ΔV _dc exceeded the specified value _C due to the discharge of the capacitor C1 as a result of the short circuit between the DC bus lines due to the ON of the upper arm switching element of the phase.
Therefore, in this case, it is determined that at least one or more switching elements of the lower arm are short-circuited and stuck, causing _a serious failure, and the initial charging relay SW1 is turned OFF to stop the operation (S110, S111).

Further, when the amount of change ΔV _dc is equal to or _less than the specified value C (Yes in S108), all the switching elements of the lower arm are OFF _. In step S109, the lower arm switching elements of all phases are simultaneously turned on for a short period of time.
After that, the same processing as in steps S108, S110 and S111 is performed to determine the presence or absence of serious failure due to short-circuit fixation of any switching element of the upper arm (steps S112, S114 and S115). Then, if the determination result in step S112 is Yes, "there is no short-circuit fixation in the lower arm switching elements, or the upper arm switching elements of all phases are open and fixation." There is no short-circuit fixation in the elements, or the lower arm switching elements of all phases are open-fixed.", and the process proceeds to Diagnosis 2 in FIG. 4 (S113).

Thus, in steps S107 to S115, it is diagnosed whether or not the switching element of the lower arm or the upper arm is short-circuited and fixed. In this regard, in the prior art of FIG. 10, it is necessary to turn ON one arm at a time (step S17, etc.) for diagnosis. Therefore, in the case of a three-phase inverter, the processing steps are reduced to 1/3.

Next, diagnosis 2 will be described with reference to FIG. This diagnosis is to detect whether or not the switching element of one of the upper and lower arms in the main circuit INV is stuck open.
First, the upper arm switching element and the lower arm switching element of different phases of the main circuit INV are combined and turned ON simultaneously for a short period of time. Here, as an example, the U-phase upper arm switching element _Qu and the V-phase lower arm switching element _Qy are simultaneously turned on (S201).
In this state, the amount of change ΔV _dc of the DC intermediate voltage V _dc is compared with a specified value D (a specified value of change amount in claims) (S202). The specified value D is set to _a value slightly larger than the amount of voltage drop due to natural discharge of the capacitor C1.
When the output currents _Iu , _Iv , and _Iw of each phase are measured as shown in FIG. 1, in step _S202 , instead of comparing _{ΔV dc} and D, - It may be determined that I _v >0.

If the switching elements Q _u and Q _y were not stuck open, two phases would flow through these switching elements Q _u and Q _y and the stator winding of the motor M, so the amount of change ΔV _dc is equal to or greater than the specified value D, which is larger _than the amount of voltage drop due to natural discharge of the capacitor C1 (S202 Yes).
Further, if the amount of change ΔV _dc is not equal to or greater than the specified value D (S202 No), it can be determined that at least one of the switching elements Q _u and Q _y is fixed open _. Fail data indicating that the test for _y (Q _u , Q _y test) has failed is stored in memory (S206).

If the amount of change ΔV _dc is equal to or greater than the specified value D (Yes in S202), neither of the switching elements Q _u and Q _y is fixed open, and the capacitor C ₁ is discharged by the two-phase conduction to discharge the DC intermediate voltage V _dc . is lowered, the initial charge relay _SW1 is turned ON again to charge the capacitor C1 ( _S203 ).
After that, similarly to steps S103 and S106 in FIG. 3, when the DC intermediate voltage _Vdc becomes equal to or higher than the specified value B (the DC voltage specified value in claims), the initial charging relay _SW1 is turned OFF (S204 Yes, S205). .

Similar to the Q _u and Q _y test (S207) described above, the V-phase upper arm switching element Q _v and the W-phase lower arm switching element Q _z are combined to perform the Q _v and Q _z test (S217). , _W -phase upper arm switching element Qw and U-phase lower arm switching element _Qx are combined to perform the _Qw , _Qx test (S227), thereby opening all the switching elements of the main circuit INV. Diagnose the presence or absence of sticking.
After that, if there is no failing data for each test, it is determined that all the switching elements are not stuck open and all the arms can be turned ON/OFF, and the initial diagnosis ends (S230 Yes, S231).
If there is unacceptable data (No at S230), it is determined that any switching element is stuck open, and the process proceeds to Diagnosis 3 to identify the switching element.
As described above, in diagnosis 2, the switching elements of the upper and lower arms of different phases are turned on for a short period of time to perform the test. A test can detect the presence or absence of an open stick.

Next, diagnosis 3 will be described. FIG. 5 shows an extracted main part of Diagnosis 3, and the details are as shown in the flow chart of FIG.
In diagnosis 3, a combination of switching elements of the upper and lower arms of different phases is generated differently from diagnosis 2, and the same test as in diagnosis 2 is performed on that combination.

For example, a U-phase upper arm switching element Q _u and a W-phase lower arm switching element Q _z are combined to perform a Q _u and Q _z test (steps S311 and S322 in FIG. 6 to be described later). The switching element Qv and the U-phase lower arm switching element _Qx are combined to perform a _Qv , _Qx test (S321, S332), and the _W -phase upper arm switching element Qw and the _V -phase lower arm switching element Q are tested. _y and _Qw , _Qy tests are performed (S312, S331).
In each test, as in step S207 of diagnosis 2 (FIG. 4), simultaneous ON of two switching elements → comparison of amount of change ΔV _dc in DC intermediate voltage with specified value D (or (monitoring of output current)→ON of initial charging relay _SW1 →Comparison between DC intermediate voltage _Vdc and specified value B→OFF of initial charging relay _SW1 and storage of failure data.

Here, FIGS. 5A and 5B show an example of a combination of upper and lower arm switching elements (dashed line) targeted for diagnosis 2 and a combination of upper and lower arm switching elements targeted for diagnosis 3 (dashed line). ) are shown. Since the fault diagnosis technique of the present invention can be applied to n-phase (n is an integer of 3 or more) _inverters , in FIGS. _Hn , and the lower arm switching elements are denoted by Q _L1 to Q _Ln .
In both FIGS. 5A and 5B, the combination (chain line) of the switching elements of the upper and lower arms targeted for diagnosis 2 is the same. are adjacent phases Q _H2 , Q _L1 and Q _H3 , Q _L2 . . . , and in FIG. ) are defined as Q _H1 , Q _L3 , Q _H2 , Q _L3 . . . with one phase in between.

In any case, diagnosis 3 tests a combination of upper and lower arm switching elements different from diagnosis 2, so as is clear from FIG. Q _u , Q _y test, Q _v , Q _z test, Q _w , Q _x test) are performed, and in diagnosis 3, a maximum of three tests (Q _u , Q _z test, Q _v , Q _x test, Q _w , Q _y test). If this is generalized to an n-phase inverter, both diagnostics 2 and 3 require a maximum of 2n tests.
In FIG. 4, three tests ( _Qu , _Qz test, _Qv , _Qx test, _Qw , _Qy test) of Diagnosis 3 are displayed in series. As _illustrated by FIG. ₆ of _FIG . _{6 , Q u} , _Qz test, _Qv , _Qx test, _Qw , _Qy test, ie, two tests. Therefore, if the tests 2 and 3 are performed five times in total, it is possible to identify the switching element stuck open.

In FIG. 4, when all the tests of Diagnosis 3 are completed, the results are compared with the failure map 500 prepared in advance to determine whether or not the vehicle can be operated (S313, S323, S333).
As a result of this determination, if the failure is such that only one arm is stuck open and can be degenerated, the switching element stuck open is identified and the initial diagnosis is completed (S314, S315, S324, S325, S334). , S335). Here, in the three-phase inverter, even if the switching element of one arm is stuck open, if the other switching elements are sound, the degeneracy operation as a single-phase inverter is possible.
Also, if the two arms are fixed open and there is a serious failure, it is determined that the vehicle cannot be operated, and the initial diagnosis is terminated (S316, S326, S336).

Specific processing contents of diagnosis 3 will be described in detail based on FIG.
As described above, as a result of performing three tests ( _Qu , _{Qy test, Qv, Qz test , Qw} , _Qx test) according to diagnosis 2, when it is diagnosed that there is open fixation (S230 No) Then, the process proceeds to Diagnosis 3 in FIG.
In FIG. 6, first, it is determined whether or not the number of failed tests is one, and if there are two or more, it is determined that multiple failures have occurred due to open fixation of multiple arms, and the initial diagnosis ends. (S301 No, S303).

If one test fails (S301 Yes), then the test is one of the three tests of diagnosis 2 ( _Qu , _{Qy test, Qv, Qz test , Qw} , _Qx test). It is determined which one it is (S302). As a result, if the failed test is the Q _u , Q _y test ( _S207 ), the processing after step _S311 is _performed . , Q _x test (S227), the processing after step S331 is executed.

For example, if the failed test is the Q _u , Q _y test (S207), the open-fixed switching elements may be only Q _u , only Q _y , or both Q _u and Q _y . However, it is determined in which case it is by the processing after step S311.
First, for the combination of the U-phase upper arm switching element Q _u and the W-phase lower arm switching element Q _z , the two switching elements are simultaneously turned ON to change the DC intermediate voltage ΔV _dc in the same manner as in step S207. Comparison with the specified value D→ON of the initial charging relay _SW1 →Comparison between the DC intermediate voltage _Vdc and the specified value B→OFF of the initial charging relay _SW1 , and saving the failure data, Q _u , Q A _z -test is executed (S311).
Similarly, a _Qw , _Qy test is performed for the combination of the _W -phase upper arm switching element Qw and the V-phase lower arm switching element _Qy (S312).
Thereafter, the results of each test are collated with the failure map 500 prepared in advance to identify the switching element stuck open and determine whether or not the operation is possible (S313).

FIG. 7 shows an example of a fault map 500. As shown in FIG. This fault map 500 shows the presence or absence of open fixation in all arms (switching elements Q _u , Q _v , Q _w , Q _x , Q _y , Q _z ) of the three-phase inverter (64 ) and each test by diagnosis 2 and 3 corresponding to each case (diagnosis 2 Q _u , Q _y test, Q _v , Q _z test, Q _w , Q _x test, and diagnosis 3 Q _u , _Qz test, _Qv , _Qx test, _Qw , _Qy test). 8 shows a case (No. 1) in which all arms are normal and all cases (No. 2 to No. 7) in which the switching element of one arm has an open failure from the failure map 500 in FIG. It is extracted from

For example, No. 2 in FIG. 8 is a _case in which only the switching _{element Qz} is _stuck open _. The result of the test (S322) is failed (no). No. 3 in FIG. 8 is a case in which only the _{switching element Qy} is _{stuck open} . The result of the test (S312) is failed (no).
Therefore, as far as the open fixation of the switching element of one arm is concerned, based on the "pass/fail by diagnosis 2 and 3" pattern (o, x pattern) in the fault map 500 of FIG. (switching elements) can be specified.

Returning to step S313, since the Q _u and Q _y test (S207) of diagnosis 2 failed, according to _FIG . 7 (Q _u stuck open) applies. In the case of No. 3, the _Qw and _Qy tests of diagnosis 3 (S312) fail, and in the case of No. 7, the _Qu and _Qz tests of diagnosis 3 (S311) are rejected. should fail.
Therefore, as shown in FIG. 6, the Q _u , Q _z test (S311) and the Q _w , Q _y test (S312) are performed, and the Q _u , Q _y test (S207) in the diagnosis 2 of FIG. By comparing the results of the three tests with the "pass/fail by diagnosis 2 and 3" column of the fault map 500 of FIG. 8, the arm that is stuck open is identified.

Specifically, if the Q _w , Q _y test (S312) fails, it can be determined that Q _y is open and stuck according to No. 3, and if the Q _u , Q _z test (S311) fails, No. 7, it can be determined that Q _u is open and fixed. Also, if both of these two tests fail (No. 3 and No. 7 are satisfied at the same time), it can be determined that both Q _u and Q _y are stuck open. .
As described above, by the processing of step S313 in FIG. 6, it is determined that one arm of Q _u or Q _y is stuck open (S314, S315), or two arms of Q _u and Q _y are stuck open (S316), and the initial End diagnostics. It should be noted that 1-arm open fixation corresponds to a minor failure, and 2-arm open fixation corresponds to a major failure.
Similarly, if the diagnostic 2 Q _v , Q _z test (S217) fails, steps S321 to _S326 of FIG. If the _Qx test (S227) fails, steps S331-S336 of FIG. 6 are executed to end the initial diagnosis.

_As is _clear from _FIG . _{6 , diagnosis} 3, by performing two tests (S311, S312, or S321, S322, or S331, S332), it is possible to identify the switching element stuck open.
In other words, in the case of a three-phase inverter, tests 2 and 3 may be performed a total of five times, and in general, in the case of an n-phase inverter, tests may be performed (n+2) times.

As in the cases of No. 63 and No. 64 in the fault map 500 of FIG. 7, there are cases where the pass/fail results of the diagnostics 2 and 3 are the same for all tests, and the switching elements other than _Qz are stuck open. (No. 63) or all the switching elements are stuck open (No. 64). However, multiple failures such as No. 63 and No. 64 are rare cases. Since it is possible to detect open fixation of one leg (upper and lower arms of the same phase) enclosed by a broken line in 2, it can be said that the usefulness of the present invention is great.

E ₁ : DC power supply C ₁ : Capacitor
SW ₁ : Initial charging relay SW ₂ : Main relay
R ₁ : Resistors Q _u , Q _v , Q _w , Q _x , Q _y , Q _z , Q _H1 to Q _Hn , Q _L1 to Q _Ln : Semiconductor switching elements INV: Inverter main circuit M: Motor 11: Current detector 12: AC current detection circuit 13: Voltage detector 14: DC intermediate voltage detection circuit 15: Fault diagnosis unit 16: Relay drive circuit 17: Gate drive circuit 500: Fault map

Claims (5)

A capacitor charged from a DC power supply through switching means, a main circuit connected to both ends of the capacitor and having a plurality of switching elements bridge-connected, and a drive signal for turning on and off the switching elements. In a power conversion device comprising a control circuit that generates
The control circuit is
The amount of change in the voltage across the capacitor when a test is conducted in which the upper arm switching element and the lower arm switching element of different phases in the main circuit are combined and these two switching elements are simultaneously turned on. performing a process of determining that at least one of the two switching elements is stuck open when the value is below a specified value and storing the test failure data;
Based on the failure data obtained by executing the processing for all the switching elements of the main circuit, it is determined that any switching element is stuck open,
When there is only one failed data,
The test and the failure data are stored by combining the switching element of the upper arm that constitutes the failure data and the switching element of the lower arm of the other phase, and the switching of the lower arm that constitutes the failure data. By combining the element and the switching element of the upper arm of the other phase, performing the test and storing the failure data, n+2 (n is the number of phases of the main circuit) pass/fail data are generated, and the pass/fail data with a failure map prepared in advance to identify a switching element stuck open . A capacitor charged from a DC power supply through switching means, a main circuit connected to both ends of the capacitor and having a plurality of switching elements bridge-connected, and a drive signal for turning on and off the switching elements. In a power conversion device comprising a control circuit that generates
The control circuit is
When the output current of one phase becomes zero in a test in which an upper arm switching element and a lower arm switching element of different phases in the main circuit are combined and these two switching elements are turned on simultaneously, the above-mentioned Determining that at least one of the two switching elements is stuck open and storing the test failure data,
Based on the failure data obtained by executing the processing for all the switching elements of the main circuit, it is determined that any switching element is stuck open ,
When there is only one failed data,
The test and the failure data are stored by combining the switching element of the upper arm that constitutes the failure data and the switching element of the lower arm of the other phase, and the switching of the lower arm that constitutes the failure data. By combining the element and the switching element of the upper arm of the other phase, performing the test and storing the failure data, n+2 (n is the number of phases of the main circuit) pass/fail data are generated, and the pass/fail data with a failure map prepared in advance to identify a switching element stuck open . In the power converter according to claim 1 or 2 ,
The control circuit is
When it is determined that none of the two switching elements that are turned on at the same time are stuck open, the capacitor is charged and the charging of the capacitor is stopped when the voltage across the capacitor reaches a DC voltage specified value or more. and power conversion equipment. In the power converter according to claim 1 ,
The control circuit is
When it is determined that any switching element is stuck open,
For all the switching elements of the main circuit, performing the test and storing the failure data for two switching elements respectively selected by a combination different from the combination of the two switching elements in claim 1. 2n pieces (n is the number of phases of the main circuit) of pass/fail data are generated, and the pass/fail data is collated with a failure map prepared in advance to identify the switching element that is stuck open . conversion device. In the power converter according to claim 2,
The control circuit is
When it is determined that any switching element is stuck open,
For all the switching elements of the main circuit, performing the test and storing the failure data for two switching elements respectively selected by a combination different from the combination of the two switching elements in claim 2. 2n pieces (n is the number of phases of the main circuit) of pass/fail data are generated, and the pass/fail data is collated with a failure map prepared in advance to identify the switching element that is stuck open. conversion device.

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